Special hypoallergenic formulas are commercially available based on hydrolyzed protein, but they can be expensive and unpalatable--infants may refuse them.
One example of such formulas is to be found in U.S. Pat. No. 4,670,268, which explains that protein hydrolysates, comprising short peptide fragments and/or free amino acids have been found to be less immunogenic or allergenic than intact proteins. The immunogenicity of the formula depends, it is stated, largely on the extent of hydrolysis of the selected protein hydrolysate, and the patent recommends that the protein hydrolysate should be extensively hydrolyzed to yield very short peptides and free amino acids.
As noted in U.S. Pat. No. 4,670,268, however, the extensively digested and hypoimmunogenic protein hydrolysates have the undesirable characteristic of loss of capacity to emulsify fat and form physically stable emulsions that do not separate during storage. As stated in U.S. Pat. No. 4,670,268, another common problem encountered in the preparation of hypoallergenic formulas is the formation of undesirable brown colour as a result of the reaction between the carbonyl groups of reducing sugars and the nitrogen-amine containing compounds such as amino acids in the formula (Maillard type reaction) especially at elevated temperatures encountered during sterilization.
In common with U.S. Pat. No. 4,414,238, which is referred to in U.S. Pat. No. 4,670,268, the use of a low dextrose equivalent hydrolyzed starch is particularly recommended to minimise Maillard type reactions and brown colour formation, and the inclusion of octenyl succinic anydride modified starch is prescribed in order to form a stable emulsion.
U.S. Pat. No. 4,670,268 recommends further supplementation of the hydrolyzed protein source with various free amino acids to provide a nutritionally balanced amino acid content.
The formulas of both U.S. Pat. Nos. 4,670,268 and 4,414,238 are primarily intended to be supplied in ready-to-use liquid form, although U.S. Pat. No. 4,670,268 mentions the possibility of concentration and of supplying in powder form for reconstitution by adding water prior to feeding.
While doubts have been raised about the use of octenyl succinic anhydride, probably the main problems with hydrolysed hypoallergenic formulas are that they could be expensive, and not always very palatable.